Method and system to avoid battery sag by detecting momentary fluctuation in a periodic terminal voltage measurement and excluding the measurement from updated average terminal voltage

ABSTRACT

A method and system for power source management of a portable device. A power source used to supply electrical energy for a portable device should ideally operate with a constant terminal voltage. However, the terminal voltage of a cell or group of cells used as a source of electrical energy can be expected to reduce in amplitude over its operational lifetime. Near the end of operational lifetime, the terminal voltage of such a source can be expected to decrease rapidly. Furthermore, the source terminal voltage will also exhibit significant variations in amplitude in response to changes in electric current demands on the source. Such source voltage variations can impair or even prevent proper operation of the electronic circuits within the portable device. Power management for proper operation of a portable device is necessary to ensure proper device operation and to prevent loss of data. The present method and system controls portable device operation by periodic determination of average source terminal voltage which is faster and simpler than continuous monitoring used with present systems. Comparison of the periodic average source terminal voltage with stored operational voltage limits allows either temporary or permanent curtailment of certain device operations. Such action can be used to prevent any loss of device data. Further, the present method offers the advantage of identifying momentary fluctuations in source terminal voltage caused by temporary demands in source current levels. Thus, continuous monitoring and prior knowledge of source load demands and equipment as required by present methods are eliminated.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of portable devices such aspersonal digital assistants or palmtop computer systems. Morespecifically, embodiments of the present invention relate to powersource management in a portable device.

2. Related Art

As the components required to build a computer system have reduced insize, new categories of electronic devices and computer systems haveemerged. One of the new categories of computer systems is the “palmtop”computer system. A palmtop computer system is a computer that is smallenough to be held in the hand of a user and can therefore be“palm-sized.” Most palmtop computer systems are used to implementvarious Personal Information Management (PIM) applications such as anaddress book, a daily organizer (calendar, datebook, etc.) andelectronic notepads, to name a few. Palmtop computers with PIM softwarehave been known as Personal Digital Assistants (PDAs). Many PDAs have asmall and flat display screen associated therewith.

User convenience and device value are very important factors forportable electronic devices. Typically, portable electronic devices areemployed while the user is on the run, e.g., in business meetings, onbusiness travel, personal travel, in a vehicle, on foot, etc. Becausethe user may be occupied or busy while using the portable electronicdevice, the number of user steps or user tasks required in order toaccess information from an electronic device (or to store informationinto the electronic device) is crucial for producing a commerciallysuccessful and useful product. That is, the more difficult it is toaccess data from an electronic device, the less likely the user willperform those tasks to obtain the information. Likewise, the easierinformation is to obtain, the more likely the portable electronic devicewill be used to obtain that information and the more likely the portableelectronic device will become a part of the user's everyday activities.

Similarly, the more useful the device, the more the device will be usedand acquired. The functionality of mobile wireless devices is undergoinga transition. Mobile devices are evolving from a single applicationdevice with a dedicated specific purpose communication channel (forexample, a cell phone or pager), to more general-purpose devices withmore flexible data communication capabilities.

More specifically, wireless technology is advancing, both in the numberof options that are available for providing connectivity, and in theflexibility to provide general purpose data communication. Differenttechnologies such as cellular technologies (e.g., CDMA, TDMA), LANaccess technologies (e.g., IEEE 802.11, HomeRF) and PAN technologies(e.g., Bluetooth, IR) each address a different set of needs, and providea different set of potential services. Mobile devices are no longerrestricted to a single communication channel. Modular mobile devicesallow network interfaces to be attached, allowing for unlimitedcommunications configurations. In addition, Bluetooth technology allowsa single mobile device to simultaneously access multiple piconetsthrough a single interface. To facilitate mobile wireless communication,several wireless modem peripheral devices are available that can bedirectly connected to the serial interface port of a host computersystem thereby providing wireless communication to the internet.

A power source composed of one or more energy storing cells isfrequently used to supply the electrical energy required for operationof a portable device such as a PDA. Such a power source must supply theneeded electrical current for the device and any attached devices, andshould ideally operate with a constant terminal voltage. However, theterminal voltage of a single cell or a group of cells (battery) used asa source of electrical energy can be expected to reduce in amplitudeover its operational lifetime. In fact, near the end of operationallifetime, the terminal voltage of such a source can be expected todecrease rapidly. Furthermore, the source terminal voltage will alsoexhibit significant variations in amplitude in response to changes inelectric current demands on the source. For example, functions such asback lighting of a display screen or activation of a radio transmitterwill add sudden increases in power source current which may causesignificant reductions in the source terminal voltage. Such sourceterminal voltage variations can impair or even prevent proper operationof the electronic circuits within the portable device, and may possiblyresult in a loss of stored data.

Power source management methods or systems used in prior art generallyemploy continuous monitoring of the source terminal voltage. However,continuous monitoring and consequent reactions to terminal voltagefluctuations as accomplished in prior art frequently place an increasedburden on software requirements which result in slower systemoperational speeds. Furthermore, in most prior art methods or systems, aknowledge of source load demands for equipment that could be attached tothe portable device is required. This is a drawback since suchinformation requires space for storage in the portable device memory.The main disadvantage here is that the power source management softwaremust continuously search for, and make any necessary adjustments for,the attachment or detachment such equipment. An additional disadvantagepresent in prior art power management methods or systems occurs becausecontinuous monitoring is required to detect any random act which mayaffect the source terminal voltage. For example, the keying of a radiotransmitter may cause a significant reduction in source terminalvoltage.

SUMMARY OF THE INVENTION

Accordingly, what is needed is a more generally applicable method orsystem that may be used to monitor characteristics of a power sourcebeing used to supply electrical energy to a portable device. Morespecifically, a method or system is needed to modify operation of aportable device by comparing the measured terminal voltage of the powersource with a set of stored operational terminal voltage limits. Inaddition, a method or system that may be incorporated into existingportable devices with ease is needed. Further, the need for a method orsystem that will react rapidly to a momentary fluctuation in powersource terminal voltage in order to preserve stored device data, and atthe same time will distinguish between momentary and permanent changesin power source terminal voltage. The need exists also for a method orsystem that is faster than present methods which utilize continuousterminal voltage averaging schemes. In addition, a method or system forpower source management of a portable device that will provide all theabove advantages without the need for a pre-existing determination ofsystem components or operation. Such a system will then be effective andwill not require reconfiguration when system components are added to orremoved from the portable device. In addition, the needed system will beeffective when a momentary fluctuation in power source terminal voltageresults from an increase in power source current which occurs due to acause such as operation of an attached wireless radio transmitter. Thiswould be an improvement over existing systems which require continuousmonitoring of devices or systems whose operation result in an increasein power source current, Embodiments of the present invention providethe above advantages and others not specifically mentioned above butdescribed in the sections to follow.

A method and system for power source management of a portable device aredescribed. A power source used to supply electrical energy for aportable device should ideally operate with a constant terminal voltage.However, the terminal voltage of a cell or group of cells used as asource of electrical energy can be expected to reduce in amplitude overits operational lifetime. Near the end of operational lifetime, theterminal voltage of such a source can be expected to decrease rapidly.Furthermore, the source terminal voltage will also exhibit significantvariations in amplitude in response to changes in electric currentdemands on the source. Such source voltage variations can impair or evenprevent proper operation of the electronic circuits within the portabledevice. Power management for proper operation of a portable device isnecessary to ensure proper device operation and to prevent loss of data.The present method and system controls portable device operation byperiodic determination of average source terminal voltage which isfaster and simpler than continuous monitoring used with present systems.Comparison of the periodic average source terminal voltage with storedoperational voltage limits allows either temporary or permanentcurtailment of certain device operations. Such action can be used toprevent any loss of device data. Further, the present method offers theadvantage of identifying momentary fluctuations in source terminalvoltage caused by temporary demands in source current levels. Thus,continuous monitoring and prior knowledge of source load demands andequipment as required by present methods are eliminated.

In one embodiment of the present invention, a power source managementprogram is stored in the memory of a portable device such as a palmtopcomputer system. The power source terminal voltage is measuredperiodically and compared with a prior stored source terminal voltage todetermine a current, updated value. If the measured terminal voltage isdetermined to be momentary, the prior stored terminal voltage value isretained as the current, updated value. Otherwise, the measured terminalvoltage is used to calculate a new value which is then stored as thecurrent, updated source terminal voltage. The updated source terminalvoltage is then compared with a number of stored operational terminalvoltage limits, and one or more system operating functions areterminated when the updated terminal voltage falls outside operationallimits. Operating functions subject to termination as the power sourceterminal voltage decreases include, but are not limited to, radiotransmitter operation, infra-red (IR) communication, display screenillumination, liquid crystal display (LCD) operation, and completesystem shut down.

Another embodiment of the present invention utilizes a power sourcemanagement program stored in the memory of a portable device such as apalmtop computer system to terminate one or more system operatingfunctions in response to any decrease in power source terminal voltage.The program periodically determines an updated power source terminalvoltage by utilizing at least one periodically measured power sourceterminal voltage. The program will distinguish between momentary andpermanent fluctuations present in measured terminal voltage values andwill eliminate momentary values when determining an updated terminalvoltage. Operating functions subject to termination as the power sourceterminal voltage decreases include, but are not limited to, radiotransmitter operation, infra-red (IR) communication, display screenillumination, liquid crystal display (LCD) operation, and completesystem shut down.

Another embodiment of the present invention includes a portable devicesuch as a palmtop computer system comprising: a memory having a databasecontaining stored operational terminal voltage limits, measured powersource terminal voltage data, operational control functions andcomputational software, wherein the memory is communicatively coupled tothe portable device; a processor operable to periodically determine andrecord an updated power source terminal voltage value based on ameasured power source terminal voltage by executing instructions storedin the memory, to distinguish and ignore a voltage source measurementhaving a momentary fluctuation, to compare an updated terminal voltagevalue with stored operational voltage limits and to activate storedoperational control functions. Operating functions subject totermination as the power source terminal voltage decreases include, butare not limited to, radio transmitter operation infra-red (IR)communication, display screen illumination, liquid crystal display (LCD)operation, and complete system shut down.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG 1A is a block diagram of an exemplary network environment includinga portable computer system in accordance with one embodiment of thepresent invention.

FIGS. 1B, 1C, 1D, 1E and 1F are block diagrams showing variousembodiments for coupling a portable computer system to other computersystems and to the internet in accordance with the present invention.

FIG. 2 is a top side perspective view of a portable computer system inaccordance with one embodiment of the present invention.

FIG. 3 is a bottom side perspective view of the portable computer systemof FIG. 2.

FIG. 4 is a block diagram of one embodiment of a portable computersystem in accordance with the present invention.

FIG. 5 is a perspective view of the cradle device for connecting theportable computer system to other systems via a communication interfacein accordance with one embodiment of the present invention.

FIG. 6 is a block diagram of one embodiment of a server, desktop orlaptop computer system in accordance with the present invention.

FIG. 7 is a terminal voltage discharge curve typical of a voltage sourceutilized to supply electrical power in a portable computer or PDA.

FIG. 8 is a flowchart showing the steps in a process for monitoring theterminal voltage of a source used to supply electrical power to aportable computer or PDA and affecting appropriate action in accordancewith the present invention.

FIG. 9 is an expanded portion of the terminal voltage discharge curve ofFIG. 7 showing the expected gradual lowering of terminal voltage withdischarge in accordance with the present invention.

FIG. 10 is an expanded portion of the terminal voltage discharge curveof FIG. 7 showing the expected gradual lowering of terminal voltage withdischarge which includes a momentary decrease in terminal voltage due toan increase in terminal current in accordance with the presentinvention.

FIG. 11 is an expanded portion of the terminal voltage discharge curveof FIG. 7 showing the expected gradual lowering of terminal voltage withdischarge which includes a continuing decrease in terminal voltage dueto an increase in terminal current in accordance with the presentinvention.

FIG. 12 illustrates steps taken by the power source management programas the power source nears complete discharge.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the present invention, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention, However, it will be recognizedby one skilled in the art that the present invention may be practicedwithout these specific details or with equivalents thereof. In otherinstances, well known methods, procedures, components, and circuits havenot been described in detail as not to unnecessarily obscure aspects ofthe present invention.

Notation and Nomenclature

Some portions of the detailed descriptions, which follow, are presentedin terms of procedures, steps, logic blocks, processing, and othersymbolic representations of operations on data bits that can beperformed on computer memory. These descriptions and representations arethe means used by those skilled in the data processing arts to mosteffectively convey the substance of their work to others skilled in theart. A procedure, computer executed step, logic block, process, etc., ishere, and generally, conceived to be a self-consistent sequence of stepsor instructions leading to a desired result. The steps are thoserequiring physical manipulations of physical quantities. Usually, thoughnot necessarily, these quantities take the form of electrical ormagnetic signals capable of being stored, transferred, combined,compared, and otherwise manipulated in a computer system. It has provenconvenient at times, principally for reasons of common usage, to referto these signals as bits, values, elements, symbols, characters, terms,numbers, or the like.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the followingdiscussions, it is appreciated that throughout the present invention,discussions utilizing terms such as “determining” or “indicating” or“indexing” or “receiving” or “performing” or “initiating” or “sending”or “implementing” or “disabling” or “enabling” or “displaying” or thelike, refer to the action and processes of a computer system or similarelectronic computing device, that manipulates and transforms datarepresented as physical (electronic) quantities within the computersystem's registers and memories into other data similarly represented asphysical quantities within the computer system memories or registers orother such information storage, transmission or display devices.

The present invention is discussed primarily in the context of aportable computer system, such as a palmtop or personal digitalassistant, with the capability to access via the Internet a World WideWeb (“Web”) site residing on a server computer system. However, it isappreciated that the present invention can be used with other types ofdevices that have the capability to access some type of central deviceor central site, including but not limited to laptop computer systems.

Exemplary Palmtop Platform

FIG. 1A is a block diagram of an exemplary network environment 50including a portable computer system 100 in accordance with oneembodiment of the present invention. Portable computer system 100 isalso known as a palmtop or palm-sized computer system or as a personaldigital assistant (PDA). In one embodiment, portable computer system 100has the ability to transmit and receive data and information over awireless communication interface (e.g., a radio interface). In oneembodiment, the wireless communication interface is integrated intoportable computer system 100; in another embodiment, the wirelesscommunication interface is accomplished with a wireless modem attachment(not shown).

In the present embodiment, base station 32 is both a transmitter andreceiver base station, which can be implemented by coupling it into anexisting public telephone network 34. Implemented in this manner, basestation 32 enables portable computer system 100 to communicate with aproxy server computer system 36, which is coupled by wire to theexisting public telephone network 34. Furthermore, proxy server computersystem 36 is coupled to the Internet 52, thereby enabling portablecomputer system 100 to communicate with the Internet 52. Coupled withInternet 52 are multiple servers exemplified by server 30. Residing onserver 30 is a Web site 40. When communicating with a Web site overInternet 52, protocols such as CTP (Compact Transport Protocol) and CML(Compact Markup Language) can be used by portable computer system 100 inthe present embodiment.

It should be appreciated that within the present embodiment, one of thefunctions of proxy server 36 is to perform operations over the Internet52 on behalf of portable computer system 100. For example, proxy server36 has a particular Internet address and acts as a proxy device forportable computer system 100 over the Internet 52.

It should be further appreciated that other embodiments of acommunications network, planned or envisioned, may be utilized inaccordance with the present invention. For example, a wirelessconnection may be made from portable computer system 100 directly to theInternet 52.

The data and information which are communicated between base station 32and portable computer system 100 are the same type of information anddata that can conventionally be transferred and received over a publictelephone wire network system. However, a wireless communicationinterface is utilized to communicate data and information betweenportable computer system 100 and base station 32. It should beappreciated that one embodiment of a wireless communication system inaccordance with the present invention is the Mobitex wirelesscommunication system.

FIGS. 1B, 1C, 1D, 1E and 1F are block diagrams showing variousembodiments of a system 51 for coupling a portable computer system 100to other computer systems and to the Internet 52 in accordance with thepresent invention. System 51 is described in the context of wiredconnections between its various devices and components; however, it isappreciated that wireless connections (such as but not limited toBluetooth wireless connections) can also be used.

With reference first to FIG. 1B, system 51 comprises a host computersystem 56 which can either be a desktop unit as shown, or,alternatively, can be a laptop system 58. Optionally, one or more hostcomputer systems can be used within system 51. Host computer systems 58and 56 are shown connected to a communication bus 54 such as an EthernetLocal Area Network (LAN), but which can instead be any of a number ofother types. Bus 54 can provide communication with the Internet 52 usinga number of well-known protocols. Coupled with Internet 52 are multipleservers exemplified by server 30. Residing on server 30 is a Web site40.

Importantly, in the present embodiment, host computer system 56 is alsocoupled via connector cable 68 to a cradle 60 for receiving andinitiating communication with portable computer system 100 (“handheldcomputer”) of the present invention. Connector cable 68 can be a serialbus (e.g., RS232), a parallel bus, a Universal Serial Bus (USB), or anyother type of workable connection. Cradle 60 provides an electrical andmechanical communication interface between connector cable 68 andportable computer system 100 for two-way communications with hostcomputer system 56. Portable computer system 100 also contains awireless infrared communication mechanism 64 for sending and receivinginformation from other devices.

With reference next to FIG. 1C, in this embodiment, laptop system 58 iscoupled via connector cable 68 to cradle 60. As described above,connector cable 68 can be a serial bus (e.g., RS232), a parallel bus, aUSB, or any other type of workable connection for enabling two-waycommunication between portable computer system 100 and laptop system 58.

FIG. 1D shows another embodiment of system 51 in accordance with thepresent invention. In this embodiment, host computer system 56 iscoupled via connector cable 68 to cradle 60. Host computer system 56 isalso coupled to a modem 76 via another connector cable 78. Connectorcable 78 can be a serial bus, a parallel bus, a USB, or any other typeof workable connection that can be used for allowing two-waycommunication between host computer system 56 and the Internet 52. Inthis embodiment, connector cable 78 is coupled with a wire line 74 to acentral office (or cable office, etc.) 81 via modem 76. Modem 76 can beinternal to or external to host computer system 56. Modem 76 can be ananalog modem, a cable modem, an ADSL (Asymmetric Digital SubscriberLine) modem, or any other such device. Central office 81 in turn iscommunicatively coupled to the Internet 52 via some type of well-knowncommunication line 84.

FIG. 1E shows another embodiment of system 51 in accordance with thepresent invention. In this embodiment, laptop system 58 is coupled viaconnector cable 68 to cradle 60. Laptop system 58 is also coupled tomodem 76 via connector cable 78. In this embodiment, connector cable 78is coupled with wire line 74 to central office 81 via modem 76. Centraloffice 81 in turn is communicatively coupled to the Internet 52 viacommunication line 84.

FIG. 1F shows another embodiment of system 51 in accordance with thepresent invention. In this embodiment, portable computer system 100 iscoupled with wire line 74 via a modem 82. In one embodiment, portablecomputer system 100 is a Palm V or other such PDA, and modem 82 is aPalm V modem or PDA modem. Wire line 74 is communicatively coupled tocentral office 81 which in turn is communicatively coupled to theInternet 52 via communication line 84.

With reference to FIGS. 1A through 1F, it is appreciated that portablecomputer system 100 can be used in a network environment combiningelements of networks 50 and 51. That is, as will be seen below, portablecomputer system 100 can include both a wireless infrared communicationmechanism and a signal (e.g., radio) receiver/transmitter device.

FIG. 2 is a perspective illustration of the top face 100 a of oneembodiment of the palmtop computer system 100 of the present invention.The top face 100 a contains a display screen 105 surrounded by a bezelor cover. A removable stylus 80 is also shown. The display screen 105 isa touch screen able to register contact between the screen and the tipof the stylus 80. The stylus 80 can be of any material to make contactwith the screen 105. The top face 100 a also contains one or morededicated and/or programmable buttons 75 for selecting information andcausing the computer system to implement functions. The on/off button 95is also shown.

FIG. 2 also illustrates a handwriting recognition pad or “digitizer”containing two regions 106 a and 106 b. Region 106 a is for the drawingof alphabetic characters therein (and not for numeric characters) forautomatic recognition, and region 106 b is for the drawing of numericcharacters therein (and not for alphabetic characters) for automaticrecognition. The stylus 80 is used for stroking a character within oneof the regions 106 a and 106 b. The stroke information is then fed to aninternal processor for automatic character recognition. Once charactersare recognized, they are typically displayed on the screen 105 forverification and/or modification.

FIG. 3 illustrates the bottom side 100 b of one embodiment of thepalmtop computer system that can be used in accordance with variousembodiments of the present invention. An extendible antenna 85 is shown,and also a battery storage compartment door 90 is shown. A communicationinterface 180 is also shown. In one embodiment of the present invention,the communication interface 180 is a serial communication port, butcould also alternatively be of any of a number of well-knowncommunication standards and protocols, e.g., parallel, SCSI (smallcomputer system interface), Firewire (IEEE 1394), Ethernet, etc.

FIG. 4 illustrates circuitry of computer system 100. Computer system 100includes an address/data bus 110 for communicating information, acentral processor 101 coupled with the bus for processing informationand instructions, a volatile memory 102 (e.g., random access memory,RAM) coupled with the bus 110 for storing information and instructionsfor the central processor 101 and a non-volatile memory 103 (e.g., readonly memory, ROM) coupled with the bus 110 for storing staticinformation and instructions for the processor 101. Computer system 100also includes an optional data storage device 104 (e.g., memory stick)coupled with the bus 110 for storing information and instructions.Device 104 can be removable. As described above, computer system 100also contains a display device 105 coupled to the bus 110 for displayinginformation to the computer user.

With reference still to FIG. 4, computer system 100 also includes asignal transmitter/receiver device 108, which is coupled to bus 110 forproviding a physical communication link between computer system 100, anda network environment (e.g., network environments 50 and 51 of FIGS. 1Athrough 1F). As such, signal transmitter/receiver device 108 enablescentral processor unit 101 to communicate wirelessly with otherelectronic systems coupled to the network. It should be appreciated thatwithin the present embodiment, signal transmitter/receiver device 108 iscoupled to antenna 85 (FIG. 3) and provides the functionality totransmit and receive information over a wireless communicationinterface. It should be further appreciated that the present embodimentof signal transmitter/receiver device 108 is well suited to beimplemented in a wide variety of ways. For example, signaltransmitter/receiver device 108 could be implemented as a modem.

In one embodiment, computer system 100 includes a communication circuit109 coupled to bus 110. Communication circuit 109 includes an optionaldigital signal processor (DSP) 120 for processing data to be transmittedor data that are received via signal transmitter/receiver device 108.Alternatively, processor 101 can perform some or all of the functionsperformed by DSP 120.

Also included in computer system 100 of FIG. 4 is an optionalalphanumeric input device 106 that in one implementation is ahandwriting recognition pad (“digitizer”) having regions 106 a and 106 b(FIG. 2), for instance. Alphanumeric input device 106 can communicateinformation and command selections to processor 101. Computer system 100also includes an optional cursor control or directing device (on-screencursor control 107) coupled to bus 110 for communicating user inputinformation and command selections to processor 101. In oneimplementation, on-screen cursor control device 107 is a touch screendevice incorporated with display device 105. On-screen cursor controldevice 107 is capable of registering a position on display device 105where the stylus makes contact. The display device 105 utilized withcomputer system 100 may be a liquid crystal display device, a cathoderay tube (CRT), a field emission display device (also called a flatpanel CRT) or other display device suitable for generating graphicimages and alphanumeric characters recognizable to the user. In thepreferred embodiment, display device 105 is a flat panel display.

FIG. 5 is a perspective illustration of one embodiment of the cradle 60for receiving the palmtop computer system 100. Cradle 60 contains amechanical and electrical interface 260 for interfacing withcommunication interface 108 (FIG. 3) of computer system 100 when system100 is slid into the cradle 60 in an upright position. Once inserted,button 270 can be pressed to initiate two-way communication (e.g., acommunication session) between computer system 100 and other computersystems coupled to serial communication 265.

Exemplary Desktop/Laptop/Server Platform

Refer now to FIG. 6 which illustrates an exemplary computer system 342with which embodiments of the present invention may be practiced.Computer system 342 exemplifies desktop computer system 56 or laptopcomputer system 58 of FIG. 1B. Computer system 342 also exemplifies aserver computer system in a computer system network (such as server 30in FIGS 1A through 1F) or a proxy server computer (e.g., proxy server 36of FIG. 1A).

Continuing with reference to FIG. 6, in general, computer system 342comprises bus 709 for communicating information, processor 701 coupledwith bus 709 for processing information and instructions, random access(volatile) memory (RAM) 702 coupled with bus 709 for storing informationand instructions for processor 701, read-only (non-volatile) memory(ROM) 703 coupled with bus 709 for storing static information andinstructions for processor 701, data storage device 704 such as amagnetic or optical disk and disk drive coupled with bus 709 for storinginformation and instructions, an optional user output device such asdisplay device 705 coupled to bus 709 for displaying information to thecomputer user, an optional user input device such as alphanumeric inputdevice 706 including alphanumeric and function keys coupled to bus 709for communicating information and command selections to processor 701,and an optional user input device such as cursor control device 707coupled to bus 100 for communicating user input information and commandselections to processor 701. Furthermore, an optional input/output (I/O)device 708 is used to couple computer system 342 to, for example, acommunication bus (e.g., communication bus 54 of FIG. 1B).

Continuing with reference to FIG. 6, display device 705 utilized withcomputer system 342 may be a liquid crystal device, cathode ray tube, orother display device suitable for creating graphic images andalphanumeric characters recognizable to the user. Cursor control device707 allows the computer user to dynamically signal the two-dimensionalmovement of a visible symbol (pointer) on a display screen of displaydevice 705. Many implementations of the cursor control device are knownin the art including a trackball, mouse, joystick or special keys onalphanumeric input device 706 capable of signaling movement of a givendirection or manner of displacement. It is to be appreciated that thecursor control 707 also may be directed and/or activated via input fromthe keyboard using special keys and key sequence commands.Alternatively, the cursor may be directed and/or activated via inputfrom a number of specially adapted cursor directing devices.

FIG. 7 is a performance curve 700 showing terminal voltage versuscapacity typical of a power source composed of a number of energy cellsused to supply electrical power required for a portable device such as aPDk The vertical axis is a segmented scale showing a range of terminalvoltage 710 between 2.5 volts and 4.5 volts. The horizontal scaleillustrates the quantity of source capacity delivered to a load 720 inmilliampere-hours (mAh). The power source illustrated here has a ratedcapacity somewhat less than 1000 mAh. The resulting curve 730demonstrates how source terminal voltage 710 reduces in magnitude as thecapacity of the source 720 to deliver power to a load is depleted. Inthe fully charged state 740, this particular source has a terminalvoltage of about 4.25 volts. Beginning discharge, the terminal voltagethen decreases rather quickly 745 to around 4.0 volts. Thereafter, theterminal voltage steadily decreases at a slower rate with discharge,until a region 750 nearing complete discharge, after which the terminalvoltage drops rapidly. This figure shows the deterioration of terminalvoltage typical of a power source used with a portable device such as aPDA, and thus illustrates the need for power source management.

FIG. 8 illustrates a flow diagram of steps 800 performed by a powermanagement program according to the present invention. It is appreciatedthat the process 800 may be implemented as software code stored incomputer readable memory unit 103 and executed by processor 101. At step805, the power management program is invoked. Initial values forcontants particular to the device (PDA) in use are recalled from memoryand used to initialize the program. Such values may include, but are notlimited to:

a) initial source terminal voltage=L

b) counter value=C

c) maximum number of bad readings=K_(m)

d) terminal voltage differential (delta filter)=K_(d)

e) operational terminal voltage limit values=T₁, T₂, T₃, T₄

At step 820, the existing source terminal voltage is read and recordedin memory as value t₁. The program proceeds to step 830 where the value(L−t₁) is computed and compared with the terminal voltage differentialK_(d). If the quantity

(L−t₁) is not greater than K_(d), then there are two possibilities:

-   -   a) t₁ is slightly less then L, which indicates normal terminal        voltage reduction with discharge;    -   b), or t₁ is greater than L—that is, the quantity (L−t₁) is        negative, which indicates the terminal voltage has actually        increased above t₁. Such would be the case for example if the        radio transmitter had been activated for a period of time, and        then deactivated. In either case a) or b), the system will        advance to step 845, wherein a new value for L is set equal to        the just measured value t₁. In the case of a), the new value for        L will be slightly lower than the prior value, as would be        expected for a slowly decreasing terminal voltage. In the case        of b), the new value for L will be considerably higher as would        be the case when a current load is suddenly removed from    -   the power source. The program will then proceed to step 850        where the count C will be set, or reset to zero.

Returning to step 830, if the quantity (L−t₁) is greater than K_(d), thechange in terminal voltage is greater than the terminal voltagedifferential K_(d). In this case the system proceeds to step 835 in aneffort to determine if this reduction in terminal voltage is a singularevent, or if it is long lasting. If the preset count C is equal to zero,it means this is a singular event and the program advances to step 840,where the count C is increased by one. The program then returns to step820, reads a new value for t₁, and repeats the process described forstep 820. Only if the quantity (L−t₁) is again greater than K_(d), willthe program advance again to step 835, showing that this is not asingular occurance. The value of count C is an indication of the numberof times this event has occured. The count C is then compared to themaximum count allowed K_(m). If C<K_(m), the program increases the valueof C by one, and returns to step 820. Only when the count C exceedsK_(m) will the program advance from step 835 to step 845 where a newvalue for L is established as the most recent value of t₁.

After determining a new value for L in step 845 and setting the count Cto zero in step 850, the program advances to step 855 to begincomparison of the latest value of L with operational terminal voltagelimit values T₁, T₂, T₃, and T₄. It is to be appreciated that in thepresent embodiment, four operational terminal voltage limit values havebeen chosen for illustrative purposes, as have the functions associatedwith them. In other embodiments, there may be more or fewer operationalterminal voltage values and the functions associated with them may bedifferent than in the present embodiment. It is noted that all of theoperational terminal voltage limit values in the present embodiment havenumerical values less than the initial terminal voltage L of the powersource, and their magnitudes are ordered as L>T₁>T₂>T₃>T₄.

Upon advancing to step 855, the most recent terminal voltage value L iscompared with T₁. If L>T₁, the program returns to step 820 and repeatsas described previously. If L<T₁, the program advances to step 860,wherein activation of a radio transmitter is prohibited. The programthen advances to step 865. In step 865, If L>T₂, the program returns tostep 820 and repeats as described previously. If L<T₂, the programadvances to step 870, wherein activation of infra-red (IR) communicationis prohibited. The program then advances to step 875 where L is comparedwith T₃. If L>T₃, the program returns to step 820 and repeats asdescribed previously. If L<T₃, the program advances to step 880 whereback lighting of the display screen is prohibited. The program thenadvances to step 885 to compare L with T₄. If L>T₄, the program returnsto step 820 and repeats as described previously. If L<T₄, the programadvances to step 890 where the display screen is deactivated and theportable unit is powered down except for functions required to preservestored data and programs.

FIG. 9 illustrates steps 900 in the power source management program thatare followed with gradual diminishment of the source terminal voltage. Aportion of the terminal voltage discharge curve 930 taken from the midregion of the curve 730 is reproduced in FIG. 9. The first operationalvoltage terminal voltage limit (T₁) 940 is located well below the curve930. In accordance with step 820, the most recent terminal voltage value(L) 950 taken in step 820 is compared with the current terminal voltagemeasurement (t₁) 960 in step 830, and it is found that (L−t₁)<K_(d). Asa result, L is set equal to the new value L=t₁ in step 845, C is set (orreset) to C=0 in step 850. After determining that L>T₁ in step 855, theprogram returns to step 820. This is the expected mode of operation inthe mid region of the terminal voltage discharge curve, where the powermanagement system periodically updates the slowly decreasing value ofterminal voltage observed in the absence of sudden changes in powersource loads.

FIG. 10 illustrates steps 1000 in the power source management programthat are followed during gradual diminishment of the source terminalvoltage in which a sudden, but momentary, current load is demanded ofthe power source. A portion of the terminal voltage discharge curve 1030taken from the mid region of the curve 730 is reproduced in FIG. 10 witha representative reduction in voltage level 1045 caused by a momentaryincrease in power source current. The first operational voltage terminalvoltage limit (T₁) 1040 is located well below the curve 1030. Inaccordance with step 820, the most recent terminal voltage value (L)1050 taken in step 820 is compared with the current terminal voltagemeasurement (t₁) 1060 in step 830, and it is found that (L−t₁)>K_(d).This indicates a large decrease in source terminal voltage and theprogram advances to step 835 where the value of C is found to be zero(C=0). This is thus the first time that this reduction in terminalvoltage is noted, so in step 840 the value of C is set to 1 (C=1), thevalue of L unchanged and the program returns to step 820. A new value ofterminal voltage (t₁) is taken 1070, and in step 830 it is again foundthat (L−t₁)>K_(d). Checking the value of C in step 835 reveals that0<C<K_(m). The reduction in terminal voltage has therefore been notedbefore, but not more than K_(m) times. Thus the program returns again tostep 820 where a new reading for t₁ is taken 1080. This value iscompared in step 830 and it is found that (L−t₁)<K_(d). This indicatesthe terminal voltage has increased to a value that is within K_(d) ofthe latest stored value of L which indicates that the prior momentaryincrease in load has been removed from the power source. The programthen advances to step 845, sets L equal to the value of t₁ taken at1080, sets C=0 in step 850, notes that L>T₁ in step 855, and returns tostep 820. By these means, the power management program of the presentinvention has determined that a sudden change in source terminal voltageis momentary, and has eliminated this momentary change from the periodicterminal voltage updates.

FIG. 11 illustrates steps 1100 in the power source management programthat are followed during gradual diminishment of the source terminalvoltage in which a sudden, extended, current load is demanded of thepower source. A portion of the terminal voltage discharge curve 1130taken from the mid region of the curve 730 is reproduced in FIG. 11 witha representative reduction in voltage level 1145 caused by an extendedincrease in power source current. The first operational voltage terminalvoltage limit (T₁) 1140 is located well below the curve 1130. Inaccordance with step 830, the most recent updated terminal voltage value(L) 1150 is compared with the current terminal voltage measurement (t₁)1160 taken in step 820, and it is found that (L−t₁)>K_(d). Thisindicates a large decrease in source terminal voltage and the progamadvances to step 835 where the value of C is found to be zero (C=0).This is thus the first time that this reduction in terminal voltage isnoted, so the value of C is set to 1 in step 840, the program leaves thevalue of L unchanged 1150 and returns to step 820. A new value ofterminal voltage (t₁) is taken 1165, and in step 830 it is again foundthat (L−t₁)>K_(d). Checking the value of C in step 835 reveals that0<C<K_(m). The reduction in terminal voltage has therefore been notedbefore, but not more than K_(m) times. Thus the program returns again tostep 820 where a new reading for t₁ is taken 1170. This value iscompared in step 830 and it is again found that (L−t₁)>K_(d). This is anindication that the terminal voltage remains at a value that is stillwell below the stored value of L. Checking the value of C in step 835reveals that C>K_(m). The reduction in terminal voltage has thereforebeen noted at least K_(m) times. The program then advances to step 845,sets L equal to the value of t₁ taken at 1170, sets C=0 in step 850,notes that L>T₁ in step 855, and returns to step 820. By these means,the power management program of the present invention has determined asudden and lasting change in source terminal voltage and has updated thecurrent value of terminal voltage L accordingly.

Referring again to FIG. 11, the power source management program thencontinues with updates to normal terminal voltage reduction as describedwith the steps taken 900 in FIG. 9 until the most recent value of L1180. In step 820, a new reading for t₁ is taken 1190. This value iscompared in step 830 and it is found that (L−t₁)<K_(d). In fact, (L−t₁)is negative, which is an indication that the terminal voltage hasincreased in value which corresponds to the removal of a current loadfrom the power source. The program then advances to step 845, sets Lequal to the value of t₁ taken at 1190, sets C=0 in step 850, notes thatL>T₁ in step 855, and returns to step 820. By these means the powersource management program of the present invention has the demonstratedability to account for a sudden increase in terminal voltage which mayoccur with the removal of or reduction in power source load current andupdate stored terminal voltage values accordingly.

FIG. 12 illustrates the steps taken 1200 by the power source managementprogram as the power source nears compete discharge. A portion of thecurve 750 taken from FIG. 7 is expanded 1230 in FIG. 12. The sourceterminal voltage is discharging as expected and the program isperiodically updating terminal voltage values as previously described inaccordance with FIG. 9. In step 830, the most recent terminal voltagevalue (L) 1250 is compared with the current terminal voltage measurement(t₁) 1260 taken in step 820, and it is found that (L−t₁)<K_(d). Theprogram advances to step 845, updates L to the most recent value of t₁,sets C=0 in step 850 and advances to step 855. In this case, it is foundthat L is now less than one of the operational voltage limits T_(x),1240. As a result, one or more of the device functions are terminated,after which the program returns to step 820 provided T_(x) (1240) is notT₄. The process is repeated, and when L is found to decrease below theoperational limit T₄, the program advances to step 890 to power down theportable device.

The preferred embodiment of the present invention, battery voltage sagavoidance algorithm for a wireless handheld device, is thus described.While appreciated that the present invention should not be construed aslimited by such embodiments, but rather construed according to the belowclaims.

1. A method of power source management for a portable device, saidmethod comprising the steps of: a) calculating and storing an updatedaverage terminal voltage for said power source by utilizing at least oneperiodic terminal voltage measurement; b) detecting a momentaryfluctuation present in said periodic terminal voltage measurement andexcluding said measurement from said updated average terminal voltage;c) comparing said updated average terminal voltage with at least oneoperational terminal voltage limit, and d) terminating at least onesystem operating function when said average terminal voltage is outsidesaid operational terminal voltage limit.
 2. The method as recited inclaim 1 wherein said power source is composed of at least one cell thatgenerates electrical energy.
 3. The method as recited in claim 1 whereinsaid portable device is a palmtop computer system.
 4. The method asrecited in claim 1 wherein said step a) comprises the step of: a1)utilizing at least one measured source terminal voltage and at least oneprior stored source terminal voltage to periodically determine and storean updated average terminal voltage for said power source.
 5. The methodas recited in claim 1 wherein said step d) comprises the step of: d1)terminating a first said at least one system operating function oftransmitting a radio signal when said average terminal voltage isoutside a first said one operational terminal voltage limit.
 6. Themethod as recited in claim 1 wherein said step d) comprises the step of:d2) terminating a second said at least one system operating function ofcommunication via infra-red (IR) when said average terminal voltage isoutside a second said one operational terminal voltage limit.
 7. Themethod as recited in claim 1 wherein said step d) comprises the step of:d3) terminating a third said at least one system operating function ofilluminating information on a display screen when said average terminalvoltage is outside a third said one operational terminal voltage limit.8. The method as recited in claim 1 wherein said step d) comprises thestep of: d4) terminating a fourth said at least one system operatingfunction of displaying information on a liquid crystal display (LCD)when said average terminal voltage is outside a fourth one saidoperational terminal voltage limit.
 9. The method as recited in claim 1wherein said step b) comprises the step of: b1) detecting said momentaryfluctuation present in said periodic terminal voltage measurement bycomparing at least two consecutive said periodic terminal voltagemeasurements.
 10. A method of power source management for a portabledevice, said method comprising the steps of: a) terminating at least onesystem operating function when the updated average power source terminalvoltage is outside at least one operational terminal voltage limit; b)determining said updated average power source terminal voltage byutilizing at least one periodically measured power source terminalvoltage, and c) eliminating said measured power source terminal voltagefrom said updated average power source terminal voltage whenever amomentary fluctuation is detected in said measured power source terminalvoltage.
 11. The method as recited in claim 10 wherein said step a)comprises the step of: a1) terminating a first said at least one systemoperating function of transmitting a radio signal when said averageterminal voltage is outside a first said one operational terminalvoltage limit.
 12. The method as recited in claim 10 wherein said stepa) comprises the step of: a2) terminating a second said at least onesystem operating function of communication via infra-red (IR) when saidaverage terminal voltage is outside a second said one operationalterminal voltage limit.
 13. The method as recited in claim 10 whereinsaid step a) comprises the step of: a3) terminating a third said atleast one system operating function of illuminating information on adisplay screen when said average terminal voltage is outside a thirdsaid one operational terminal voltage limit.
 14. The method as recitedin claim 10 wherein said step a) comprises the step of: a4) terminatinga fourth said at least one system operating function of displayinginformation on a liquid crystal display (LCD) when said average terminalvoltage is outside a fourth said one operational terminal voltage limit.15. The method as recited in claim 10 wherein said power source iscomposed of at least one cell that generates electrical energy.
 16. Themethod as recited in claim 10 wherein said portable device is a palmtopcomputer system.
 17. The method as recited in claim 10 wherein said stepb) comprises the step of: b1) utilizing at least one measured sourceterminal voltage and at least one prior stored source terminal voltageto periodically determine and store an updated average terminal voltagefor said power source.
 18. The method as recited in claim 10 whereinsaid step c) comprises the step of: c1) detecting said momentaryfluctuation present in said periodic terminal voltage measurement bycomparing at least two consecutive said periodic terminal voltagemeasurements.
 19. A system for power source management of a portabledevice, said system comprising: a device having a database comprisingstored operational terminal voltage limits, measured power sourceterminal voltage data, operational control functions, and computationalsoftware, wherein said device is communicatively coupled to saidportable device; wherein said device is operable to periodically measuresaid power source terminal voltage and determine an updated averageterminal voltage; wherein said device is operational to detect amomentary fluctuation in said measured power source terminal voltage andexclude said measurement from said updated average terminal voltagedetermination, and wherein said device is operable to compare saidupdated average terminal voltage with said stored operational terminalvoltage limits and to activate said stored operational controlfunctions.
 20. The system of claim 19 wherein said portable device is apalmtop computer system.
 21. The system of claim 19 wherein said powersource is composed of at least one cell that generates electricalenergy.
 22. The system of claim 19 wherein said stored operationalcontrol functions include at least one command to terminate a systemoperation.